Signature
DW_j_star = DW_12 * DW_j / (DW_1 + DW_2)
| Inputs | Definition | Unit |
|---|---|---|
DW_12 | Combined weight for the person with both conditions (HE-FM-DWT-002) | none |
DW_j | Stand-alone weight of condition j, equal to DW_1 or DW_2 | none |
DW_1 | Stand-alone weight of condition 1 | none |
DW_2 | Stand-alone weight of condition 2 | none |
DW_j_star | Share of the combined weight assigned to condition j for cause-specific YLDs | none |
|---|
Function
Disability weight scaling of time lived with a non-fatal health state
Maps time lived in a non-fatal health state to healthy time lost by multiplying it by the state's disability weight, on a scale where 0 is equivalent to full health and 1 to death. The products give years lived with disability (YLD), which add to years of life lost to give DALYs. When people have several conditions, weights are combined multiplicatively and the combined loss is shared among the conditions. The notation follows the Disability Weight article.
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Implementations
Excel
Attributed share of a combined weight from named cells
With CombinedWeight, the condition's own weight in OwnWeight and the two stand-alone weights in WeightOne and WeightTwo, the formula returns the attributed share, held in AttributedWeight.
=CombinedWeight*OwnWeight/(WeightOne+WeightTwo)
Assumptions
Apportioning in proportion to stand-alone weights
GBD 2010 apportioned the combined weight to each contributing sequela in proportion to its weight on its own; other sharing rules give other cause-specific totals with the same overall total.
Worked examples
Condition A's share of the combined weight of 0.37
Condition A's share is 0.37 x 0.10 / 0.40, or 0.0925, so its 50 comorbid cases add 4.625 YLDs to the 95 from people with A only, 99.625 in all, as in the article.
DW_12 = 0.37; DW_j = 0.1; DW_1 = 0.1; DW_2 = 0.3; DW_j_star = 0.0925
Condition B's share of the combined weight of 0.37
Condition B's share is 0.37 x 0.30 / 0.40, or 0.2775; with 135 YLDs from people with B only, its YLDs are 148.875 and, with 80 years of life lost, its DALYs 228.875, as in the article.
DW_12 = 0.37; DW_j = 0.3; DW_1 = 0.1; DW_2 = 0.3; DW_j_star = 0.2775
Common errors
Reading the attributed disability weight share as the gain from treatment
Relieving condition B in a person who also has A lowers the weight from 0.37 to 0.10, a gain of 0.27, not the 0.2775 attributed to B; DALYs averted use the change in weight (HE-FM-DWT-005).
Sources
Combined weight apportioned in proportion to stand-alone weights
Vos T, Flaxman AD, Naghavi M, et al. Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010. The Lancet. 2012;380(9859):2163-2196. doi:10.1016/S0140-6736(12)61729-2. Methods: the combined disability weight from the co-occurrence of sequelae was apportioned to each of the contributing sequelae in proportion to the disability weight of a sequela on its own.
Canonical Identity
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